Solid phase change ink melter assembly and phase change ink image producing machine having same

ABSTRACT

A solid phase change ink melter assembly is provided in a phase change ink image producing machine. The solid phase change ink melter assembly includes (a) a melter housing having walls defining a melting chamber; and (b) a positive temperature coefficient (PTC) heating device mounted within the melting chamber for heating and melting solid pieces of phase change ink into melted molten liquid ink.

RELATED CASE

[0001] This application is related to U.S. application Ser. No. ______(Applicants' Docket NO. D/A2538) entitled “HIGH SHEAR BALL CHECK VALVEDEVICE AND A LIQUID INK IMAGE PRODUCING MACHINE USING SAME”; and U.S.application Ser. No. ______ (Applicants' Docket NO. D/A2366Q) entitled“PHASE CHANGE INK MELTING AND CONTROL APPARATUS AND METHOD AND A PHASECHANGE INK IMAGE PRODUCING MACHINE HAVING SAME”; and U.S. applicationSer. No. ______ (Applicants' Docket NO. D/A2366Q1) entitled “SOLID PHASECHANGE INK PRE-MELTER ASSEMBLY AND A PHASE CHANGE INK IMAGE PRODUCINGMACHINE HAVING SAME”, each of which is being filed herewith on the sameday and having at least one common inventor.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to image producing machines, andmore particularly to a solid phase change ink melter assembly and aphase change ink image producing machine or printer having same.

[0003] In general, phase change ink image producing machines or printersemploy phase change inks that are in the solid phase at ambienttemperature, but exist in the molten or melted liquid phase (and can beejected as drops or jets) at the elevated operating temperature of themachine or printer. At such an elevated operating temperature, dropletsor jets of the molten or liquid phase change ink are ejected from aprinthead device of the printer onto a printing media. Such ejection canbe directly onto a final image receiving substrate, or indirectly ontoan imaging member before transfer from it to the final image receivingmedia. In any case, when the ink droplets contact the surface of theprinting media, they quickly solidify to create an image in the form ofa predetermined pattern of solidified ink drops.

[0004] An example of such a phase change ink image producing machine orprinter, and the process for producing images therewith onto imagereceiving sheets is disclosed in U.S. Pat. No. 5,372,852 issued Dec. 13,1994 to Titterington et al. As disclosed therein, the phase change inkprinting process includes raising the temperature of a solid form of thephase change ink so as to melt it and form a molten liquid phase changeink. It also includes applying droplets of the phase change ink in aliquid form onto an imaging surface in a pattern using a device such asan ink jet printhead. The process then includes solidifying the phasechange ink droplets on the imaging surface, transferring them the imagereceiving substrate, and fixing the phase change ink to the substrate.

[0005] Conventionally, the solid form of the phase change is a “stick”,“block”, “bar” or “pellet” as disclosed for example in U.S. Pat. No.4,636,803 (rectangular block 24, cylindrical block); U.S. Pat. No.4,739,339 (cylindrical block); U.S. Pat. No. 5,038,157 (hexagonal bar);U.S. Pat. No. 6,053,608 (tapered lock with a stepped configuration).Further examples of such solid forms are also disclosed in designpatents such as U.S. Pat. No. D453,787 issued Feb. 19, 2002. In use,each such block form “stick”, “block”, “bar” or “pellet” is fed into aheated melting device that melts or phase changes the “stick”, “block”,“bar” or “pellet” directly into a print head reservoir for printing asdescribed above.

[0006] Conventionally, phase change ink image producing machines orprinters, particularly color image producing such machines or printers,are considered to be low throughput, typically producing at a rate ofless than 30 prints per minute (PPM). The throughput rate (PPM) of eachphase change ink image producing machine or printer employing solidphase change inks in such “stick”, “block”, “bar” or “pellet” forms isdirectly dependent on how quickly such a “stick”, “block”, “bar” or“pellet” form can be melted down into a liquid. The quality of theimages produced depends on such a melting rate, and on the types andfunctions of other subsystems employed to treat and control the phasechange ink as solid and liquid, the imaging member and its surface, theprintheads, and the image receiving substrates.

[0007] There is therefore a need for a relatively high-speed (greaterthan “XX” PPM) phase change ink image producing machine or printer thatis also capable of producing relatively high quality images,particularly color images on plain paper substrates.

SUMMARY OF THE INVENTION

[0008] In accordance with the present invention, there is provided asolid phase change ink melter assembly is provided in a phase change inkimage producing machine. The solid phase change ink melter assemblyincludes (a) a melter housing having walls defining a melting chamber;and (b) a positive temperature coefficient (PTC) heating device mountedwithin the melting chamber for heating and melting solid pieces of phasechange ink into melted molten liquid ink

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the detailed description of the invention presented below,reference is made to the drawings, in which:

[0010]FIG. 1 is a vertical schematic of the high-speed phase change inkimage producing machine or printer including the solid phase change inkmelter assembly of the present invention;

[0011]FIG. 2 is a partially exploded perspective view of the melting andcontrol system including the solid phase change ink melter assembly ofthe present invention;

[0012]FIG. 3 is a perspective, partially exploded view of the solidphase change ink melter assembly FIG. 2; and

[0013]FIG. 4 is a perspective illustration of the PTC heater of thesolid phase change ink melter assembly in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] While the present invention will be described in connection witha preferred embodiment thereof, it will be understood that it is notintended to limit the invention to that embodiment. On the contrary, itis intended to cover all alternatives, modifications, and equivalents asmay be included within the spirit and scope of the invention as definedby the appended claims.

[0015] Referring now to FIG. 1, there is illustrated an image producingmachine, such as the high-speed phase change ink image producing machineor printer 10 of the present invention. As illustrated, the machine 10includes a frame 11 to which are mounted directly or indirectly all itsoperating subsystems and components, as will be described below. Tostart, the high-speed phase change ink image producing machine orprinter 10 includes an imaging member 12 that is shown in the form of adrum, but can equally be in the form of a supported endless belt. Theimaging member 12 has an imaging surface 14 that is movable in thedirection 16, and on which phase change ink images are formed.

[0016] The high-speed phase change ink image producing machine orprinter 10 also includes a phase change ink delivery subsystem 20 thathas at least one source 22 of one color phase change ink in solid form.Since the phase change ink image producing machine or printer 10 is amulticolor image producing machine, the ink delivery system 20 includesfour (4) sources 22, 24, 26, 28, representing four (4) different colorsCYMK (cyan, yellow, magenta, black) of phase change inks. The phasechange ink delivery system also includes the melting and controlapparatus (FIG. 2) for melting or phase changing the solid form of thephase change ink into a liquid form, and then supplying the liquid formto a printhead system 30 including at least one printhead assembly 32.Since the phase change ink image producing machine or printer 10 is ahigh-speed, or high throughput, multicolor image producing machine, theprinthead system includes four (4) separate printhead assemblies 32, 34,36 and 38 as shown.

[0017] As further shown, the phase change ink image producing machine orprinter 10 includes a substrate supply and handling system 40. Thesubstrate supply and handling system 40 for example may includesubstrate supply sources 42, 44, 46, 48, of which supply source 48 forexample is a high capacity paper supply or feeder for storing andsupplying image receiving substrates in the form of cut sheets forexample. The substrate supply and handling system 40 in any caseincludes a substrate handling and treatment system 50 that has asubstrate pre-heater 52, substrate and image heater 54, and a fusingdevice 60. The phase change ink image producing machine or printer 10 asshown may also include an original document feeder 70 that has adocument holding tray 72, document sheet feeding and retrieval devices74, and a document exposure and scanning system 76.

[0018] Operation and control of the various subsystems, components andfunctions of the machine or printer 10 are performed with the aid of acontroller or electronic subsystem (ESS) 80. The ESS or controller 80for example is a self-contained, dedicated mini-computer having acentral processor unit (CPU) 82, electronic storage 84, and a display oruser interface (Ul) 86. The ESS or controller 80 for example includessensor input and control means 88 as well as a pixel placement andcontrol means 89. In addition the CPU 82 reads, captures, prepares andmanages the image data flow between image input sources such as thescanning system 76, or an online or a work station connection 90, andthe printhead assemblies 32, 34, 36, 38. As such, the ESS or controller80 is the main multi-tasking processor for operating and controlling allof the other machine subsystems and functions, including the machine'sprinting operations.

[0019] In operation, image data for an image to be produced is sent tothe controller 80 from either the scanning system 76 or via the onlineor work station connection 90 for processing and output to the printheadassemblies 32, 34, 36, 38. Additionally, the controller determinesand/or accepts related subsystem and component controls, for examplefrom operator inputs via the user interface 86, and accordingly executessuch controls. As a result, appropriate color solid forms of phasechange ink are melted and delivered to the printhead assemblies.Additionally, pixel placement control is exercised relative to theimaging surface 14 thus forming desired images per such image data, andreceiving substrates are supplied by anyone of the sources 42, 44, 46,48 and handled by means 50 in timed registration with image formation onthe surface 14. Finally, the image is transferred within the transfernip 92, from the surface 14 onto the receiving substrate for subsequentfusing at fusing device 60.

[0020] Referring now to FIGS. 1-4, the melter assembly 300 of thepresent invention is further illustrated in greater detail. As shown,each color ink CYMK (represented by the letters A, B, C, D) has a melterassembly 300, and description of one will suffice as a description ofeach of the others. Each melter assembly 300 includes a housing 302 thathas walls 304 defining a melting chamber 306. Each melter assembly 300also includes a positive temperature coefficient (PTC) heating device310 that is mounted within the melting chamber 306 for heating andmelting solid pieces of phase change ink to turn them into melted moltenliquid ink. Each melter housing 302 also includes an electricallyinsulative member 312 between the PTC heating device 310 and a base 308of the melter housing. Each housing 302 further includes a screen device314 that is mounted below the PTC heating device 310 as shown forremoving unwanted particles from the melted molten liquid ink comingfrom the heating device 310.

[0021] The PTC heating device 310 is comprised of a device frame 316made of a conductive material such as aluminum, a pill portion 320, anda folded fin 322, 324 that is also made of a conductive material such asaluminum. The folded fin 322, 324 acts as a heating element forproviding the heat and melting surface area that contact and melt thesolid pieces phase change ink. As shown, the PTC heating device includesa pair 322, 324 of the folded fins, with one mounted to each side of thepill portion 320. The pill portion 320 is formed and set forself-regulating or controlling the PTC heating device 310 at a controltemperature Tc of about 170° C. which is calculated to be significantlyhigher than a melting temperature Tm (110° C.) of the solid phase changeink. The pill portion 320 is made for example of strontium titanate, andis of the open loop type, meaning that its performance is affected bythe material temperature Tw of the solid pieces of phase change inkbeing heated.

[0022] In general, PTC heaters function as self-regulating heatingelements. They can operate at a nearly constant temperature over a broadrange of voltage and current dissipation conditions. PTC heaters as suchcan be manufactured in many different shapes such as discs, rectangles,squares, cylinders, and various other shapes, and each shape can includeholes or passages for increasing heating surface area.

[0023] As shown in FIGS. 3-4, the PTC heating device 310 of the presentinvention includes a pair of electrodes 326, 328 that are connected tothe folded fins 322, 324. In addition, each folded fin 322, 324 definesthrough-passages or channels 330, which are located between each pair offin folds 332 for example. The folded aluminum fins 322, 324 are notcoated so as to allow for maximum heat transfer, and function to keepthe solid pieces of ink separated during melting. This preventscoalescing of such pieces, which ordinarily would lump together and tendto clog the PTC heating device, as well as tend to increase the actualmelting times. The folded fins 322, 324 also serve to increase themelting surface area, thus making the PTC heating device 310 moreefficient.

[0024] The PTC heating device 310 is self-regulating because it canswitch from a low resistance to a very high resistance as itstemperature Ti and the temperature Tw of the solid pieces of phasechange ink reach a prescribed limit. Switching off the current flow tothe heating elements or folded fins 322, 324 effectively allows them tothen cool. However, the temperature of the folded fins 322, 324, willremain at the control temperature Tc as long as current is beingsupplied to them, but the steady state current will remain at a reducedlevel in a no load (that is, no solid ink) condition.

[0025] However, when more and new solid pieces of phase change ink at acooler temperature Tw are added onto the folded fins 322, 324 causingtheir temperature Ti to again drop below the control temperature Tc,current flow to the folded fins 322, 324 again resumes. In thisapplication it is advantageous to keep solid pieces of phase change inkbeing melted at a material temperature Tw of about 160° C. The pillportion designed/compounded temperature of about 170° C. is thereforeslightly higher than the expected material temperature of 160° C. Thetemperature of the folded fins 322, 324 however will drop to the heat offusion temperature of the ink, which is about 110° C. during the meltprocess. The PTC heating device 310 consumes maximum power only whenmelting is occurring, after which power consumption drops to about 15%of the maximum power.

[0026] Each melter housing 302 is electrically insulative and thusserves to isolate the PTC heating device 310 from electrically shortingout on the aluminum frame 316 of the heating device 310. The PTC heatingdevice 310 of the present invention for example uses 70 volts forraising the temperature Ti of the folded fins 322, 324 to 170° C. Thisis sufficient for heating and melting solid pieces of phase change inkthat make direct or indirect contact with the folded fins 322, 324.

[0027] The PTC temperature Ti rise time to the 170° C. is desirably lessthan 5 seconds and therefore results in immediate melting of the solidpieces of phase change ink making contact therewith. The materialtemperature Tw of the solid pieces of phase change ink first rises tothe ink's heat of fusion at 110° C. where it remains while the solidpieces melt to form a molten liquid ink.

[0028] The molten liquid ink then drops gravitationally from the foldedfins 322, 324 and through the passages or channels 330 to the moltenliquid ink storage and control assembly 400 located below the melterassembly 300 (FIG. 2). Since the molten ink drop is gravitational, theresidence time against the folded—fins 322, 324 is relatively low orshort.

[0029] The melter assembly 300 also includes a heat retaining frame 220for melting away solid ink pieces from the wall 302 in order to preventink build up on the inside walls of the melter housing. Such a build upordinarily will interfere with solid ink pieces reaching the heatingdevice 310. The pieces are melted by making contact with the heatretaining frame 220 which is made for example of aluminum, and islocated peripherally within the melter housing 302. The heat retainingframe 220 is heated by the heat conduction through the fins makingcontact, and by convection losses of the melter assembly 300 andoperates to keep melting solid pieces of ink away from the inside wallsof the melter housing 302. Periodically when solid ink pieces have beenfed to through the pre-melter assembly 200 to the melter assembly 300,the heating device (not shown) of the melter assembly will be turned onand kept on until the solid ink pieces are sufficiently melted. Thisensures that the feed pipes 206A, 206B, 206C, 206D leading to the melterassembly 300 do not clog, and that melted ink does not coalesce on theinside walls of melter housing 302.

[0030] As can be seen, there has been provided a solid phase change inkmelter assembly is provided in a phase change ink image producingmachine. The solid phase change ink melter assembly includes (a) amelter housing having walls defining a melting chamber; and (b) apositive temperature coefficient (PTC) heating device mounted within themelting chamber for heating and melting solid pieces of phase change inkinto melted molten liquid ink

[0031] While the embodiment of the present invention disclosed herein ispreferred, it will be appreciated from this teaching that variousalternative, modifications, variations or improvements therein may bemade by those skilled in the art, which are intended to be encompassedby the following claims:

What is claimed is:
 1. A solid phase change ink melter assembly in aphase change ink image producing machine, the solid phase change inkmelter assembly comprising: (a) a melter housing having walls defining amelting chamber; and (b) a positive temperature coefficient (PTC)heating device mounted within said melting chamber for heating andmelting solid pieces of phase change ink into melted molten liquid ink.2. The solid phase change ink melter assembly of claim 1, including aheat retaining frame mounted peripherally within said melter housing forkeeping solid pieces of phase change ink away from inside walls of saidmelter housing, and for preventing melted ink from coalescing againstsaid inside walls of said melter housing.
 3. The solid phase change inkmelter assembly of claim 1, including an electrically insulative memberbetween said PTC heating device and a base of said melter housing. 4.The solid phase change ink melter assembly of claim 1, including ascreen device mounted below said PTC heating device for removingunwanted particles from the melted molten liquid ink.
 5. The solid phasechange ink melter assembly of claim 1, wherein said PTC heating deviceincludes a device frame, a pill portion, and a folded fin heatingelement for providing the heat and melting surface area for contactingand melting said solid pieces phase change ink.
 6. The solid phasechange ink melter assembly of claim 5, wherein said pill portion is madeof strontium titanate.
 7. The solid phase change ink melter assembly ofclaim 5, including a pair of said folded fin heating elements onemounted to each side of said pill portion.
 8. The solid phase change inkmelter assembly of claim 5, wherein said device frame is made ofaluminum.
 9. The solid phase change ink melter assembly of claim 5,wherein said folded fin heating element is made of aluminum.
 10. Thesolid phase change ink melter assembly of claim 6, wherein a meltingtemperature for said solid pieces of phase change ink is 110° C. andsaid control temperature is 170° C.
 11. A phase change ink imageproducing machine comprising: (a) a control subsystem for controllingoperation of all subsystems and components of the image producingmachine; (b) a movable imaging member having an imaging surface; (c) aprinthead system connected to said control subsystem for ejecting dropsof melted molten liquid phase change ink onto said imaging surface toform an image; (d) ink supply sources for supplying solid pieces ofphase change ink to be heated and melted; and (d) a melter assembly forheating and melting said solid pieces of phase change ink into meltedmolten liquid ink, the melter assembly including: (i) a melter housinghaving walls defining a melting chamber; and (ii) a positive temperaturecoefficient (PTC) heating device mounted within said melting chamber forheating and melting solid pieces of phase change ink into melted moltenliquid ink.
 12. The solid phase change ink melter assembly of claim 11,including a screen device mounted below said PTC heating device forremoving unwanted particles from the melted molten liquid ink.
 13. Thesolid phase change ink melter assembly of claim 11, including anelectrically insulative member between said PTC heating device and abase of said melter housing.
 14. The solid phase change ink melterassembly of claim 11, including a heat retaining frame mountedperipherally within said melter housing for keeping solid pieces ofphase change ink away from inside walls of said melter housing, and forpreventing melted ink from coalescing against said inside walls of saidmelter housing.
 15. The solid phase change ink melter assembly of claim11, wherein said PTC heating device includes a device frame, a pillportion, and a folded fin heating element for providing the heat andmelting surface area for contacting and melting said solid pieces phasechange ink.
 16. The solid phase change ink melter assembly of claim 15,wherein said pill portion is made of strontium titanate.
 17. The solidphase change ink melter assembly of claim 15, including a pair of saidfolded fin heating elements one mounted to each side of said pillportion.
 18. The solid phase change ink melter assembly of claim 15,wherein said device frame is made of aluminum.
 19. The solid phasechange ink melter assembly of claim 15, wherein said folded fin heatingelement is made of aluminum.
 20. The solid phase change ink melterassembly of claim 16, wherein a melting temperature for said solidpieces of phase change ink is 110° C. and said control temperature is170° C.